The major objective of this research program is to elucidate factors which control the time course of ionic conductance change at the vertebrate motor endplate during neuromuscular transmission and during sustained application of acetylcholine or its stable analogue, carbamylcholine. Of particular interest is the site of action and mechanism by which Ca2+ regulates the activation-desensitization sequence at the vertebrate motor end-plate. The specific projects proposed for the upcoming grant period include a) the interaction between membrane voltage and Ca2+ in end-plate desensitization and b) the kinetics of recovery from desensitization at the neuromuscular junction. In addition, a third study which concerns morphological and electrophysiological investigation of the influence of tetraphenylboron on the motor nerve terminal will also be undertaken.